The Refraction shading model simulates how light bends and scatters as it passes through transparent or translucent materials. It allows you to create realistic glass, water, and similar surfaces by distorting light rays and tinting color based on depth. Use cases include:
- Transparent materials such as glass, ice, or water.
- Semi-translucent surfaces like frosted glass or thin plastic.
- Stylized effects requiring light distortion.
This shading model can use four texture inputs:
- Depth Map (Grayscale): Controls light absorption and tinting, simulating thickness. Thicker areas absorb or scatter more light.
- Scatter Map (RGB): Defines how light diffuses inside the material, creating effects such as translucency or soft internal glow.
- Mask Map (Grayscale): Determines which areas are refractive (white) versus opaque (black), allowing partial or selective refraction.
- Refractive Index Map (Grayscale): Specifies how much light bends when entering or exiting the surface. Higher values produce stronger refraction and reflection effects.
| Setting | Description |
|---|---|
| Depth Map Texture Slot | Add a thickness texture by clicking on the slot or dragging and dropping one from the Library. |
| Use Albedo | The depth at which tint is realized due to absorption. Lower values mean more absorption and, thus, a darker and more opaque appearance. A value of zero disables absorption & scattering. |
| Depth Value (cm) | The depth at which tint is realized due to absorption. Lower values mean more absorption and, thus, a darker and more opaque appearance. A value of zero disables absorption & scattering. |
| Depth Color | A color tint for light passing through the object. |
| Scatter Map Texture Slot | Add a scatter texture by clicking on the slot or dragging and dropping one from the Library. |
| Scatter Value | Controls the amount of scattering of light passing through the object. |
| Scatter Color | Determines the scattering color of light passing through the object. |
| Scatter Anisotropy | DSpecifies the primary direction of scattering, either forward or backward. A value of zero is even, isotropic scattering. |
| Roughness Bias | Modifies refraction roughness. Positive values make refraction rougher than reflection, while negative values make refraction less rough. |
| Distortion Limit | Lower values limit the distortion effect in rasterized views, which is often useful for thin lenses. This setting does not affect ray traced renders. |
| Mask Map Texture Slot | Add a refraction mask texture by clicking on the slot or dragging and dropping one from the Library. |
| Channel Selection | Determines which channel of the texture map will be used. It’s useful when, instead of using multiple single textures, you use one texture with different grayscale maps in the different texture channels: Red, Green, Blue, and Alpha. |
| Mask | Sets the mask value that determines the strength of transmission. When a mask map is loaded, this value should be set to 1. |
| Invert | Inverts the mask value so that darker pixels correspond to stronger transmission. |
| Use Albedo Alpha | Uses the material’s albedo alpha value to provide a transmission mask. |
| Strict Normals | Use geometric normal to decide if a ray points towards the inside or outside of the mesh. Enabling this option might help with light leaks on low poly or poorly tessellated meshes. Applies only to ray tracing. |
| Derive Refractive Index from Reflectivity | Automatically derive index of refraction from Reflectivity. Uncheck this box to override with the index value above. |
| Refractive Index Texture Slot | Add a refraction index texture by clicking on the slot or dragging and dropping one from the Library. |
| Refractive Index Value | Sets the index of refraction. Higher values will distort light to a greater degree but won’t affect surface reflectivity. |
Listed below are a number of refractive index values for reference:
| Setting | Value |
|---|---|
| Vacuum | 1.0000 |
| Air | 1.0003 |
| Ice | 1.309 |
| Water | 1.333 |
| Ethyl Alcohol | 1.361 |
| Teflon | 1.38 |
| Fluorite | 1.434 |
| Glycerine | 1.473 |
| Benzene | 1.501 |
| Plexiglas | 1.51 |
| Crown Glass | 1.52 |
| Light Flint Glass | 1.58 |
| Polycarbonate Glass | 1.59 |
| Dense Flint Glass | 1.66 |
| Sapphire gemstone | 1.77 |
| Zircon | 1.923 |
| Diamond | 2.417 |
| Rutile | 2.907 |
| Gallium phosphide | 3.50 |
